The present invention relates to an electrophotographic recording material comprising an electrically conducting film base; an optional, adhesion-promoting, insulating intermediate layer; and at least one binder-containing photoconductive film which also contains a charge-carrier generating compound and a pyrazoline derivative as a charge-transporting compound. The present invention relates particularly to a recording material in which the photoconductive film is comprised of a charge-carrier generating and charge-transport film.
The use as photoconductors of 1,3,5-triphenylpyrazoline derivatives and 1,5-diphenyl-3-styrylpyrazoline derivatives is known. Thus, in German Pat. No. 1,060,714 (corresponding to U.S. Pat. No. 3,180,729) these compounds are described in a monolayer arrangement that is characterized by homogeneous dyestuff sensitization achieved, for example, by addition of rhodamines, and that especially contains alkalinely decoatable binders. This results, however, in photoconductive films with low photosensitivity unsuitable for copying purposes.
German Pat. No. 2,220,408 (corresponding to U.S. Pat. No. 3,973,959) discloses the use of pyrazoline derivatives as charge-transport compounds in photoconductive films.
The application of 1,5-diphenyl-3-styrylpyrazoline derivatives which have electron-donating substituents such as methoxy, ethoxy, dimethylamino and diethylamino groups in the p-position of the 3-styryl and 5-phenyl group is further known from U.S. Pat. No. 3,837,851, No. 4,030,923, No. 4,307,167 and No. 4,490,452. 1-phenyl-3-[p-diethylaminostyryl)-5-(p-diethylaminophenyl)]pyrazoline is perferably used in transport films.
In addition, similar pyrazoline derivatives in photoconductive films are known from U.S. Pat. No. 4,278,746. Analogous compounds are also described in U.S. Pat. No. 4,315,982.
A disadvantage of the known pyrazoline derivatives is, in some cases, their poor yield during manufacture and their difficult preparation, involving several reaction stages.
In German Pat. No. 3,246,036 (corresponding to U.S. Pat. No. 4,567,125), 1,5-diphenyl-3-p-methoxyphenylpyrazoline and 1-phenyl-3-p-methylstyryl-5-p-tolylpyrazoline are described in charge-transport films. The latter compound tends to crystalline out after film formation and, in addition, its adhesion and photosensitivity are still not very satisfactory.